1. Field of the Invention
The present invention relates to a power unit for a saddle-type vehicle in which gear trains of a plurality of shift stages one of which is selectively established according to the rotation of a shift drum are provided in a power train system between a drive source that exerts a driving force and a drive wheel. A change mechanism that rotates the shift drum includes a shift spindle that rotates according to the input of a gear shifting operating force and a shift arm that engages with a locking pin provided on the shift drum side and is fixed to the shift spindle. A detection shaft of a shift position sensor that detects the rotational position of the shift drum is interlocked and connected with the shift drum.
2. Description of Background Art
Such a power unit for a saddle-type vehicle is known. See, for example, Japanese Patent Laid-Open No. 2011-196433. In this power unit, an interlocking shaft coaxial with the rotational axis line of the shift drum is disposed so as to penetrate the shift arm in order to be interlocked and connected with the shift position sensor. Because the shift arm swings, an insertion hole with an arc shape for allowing the interlocking shaft to penetrate therethrough is made in the shift arm. The insertion hole is larger than the interlocking shaft in size. Meanwhile, the shift arm is engaged with the locking pin on the shift drum side, and the locking pin is engaged with a concave part formed in matching with the outer diameter of the locking pin by bending the tip part of the shift arm in order to ensure the rigidity of the shift arm.
However, as disclosed in the above-mentioned Japanese Patent Laid-Open No. 2011-196433, in the structure in which the locking pin is engaged with the concave part formed in the shift arm, there is a possibility that friction increases are attributed to the pressing of the shift arm by the locking pin in the axial direction. For smoother gear shifting, a structure in which the shift arm is engaged with the locking pin with a surface with less friction is preferable. However, there is a concern that the rigidity of the shift arm lowers if merely an engagement hole for engagement with the locking pin is formed in the shift arm having the arc-shaped insertion hole in which the interlocking shaft to be interlocked and connected the shift position sensor is inserted.